Round Amounts Heuristic

The Round Amounts Heuristic, otherwise known as the Change Output Heuristic is used in chain analysis to attempt to determine which outputs of a transaction are sending to another party and which are returning bitcoin to the sender as change. This heuristic analyses the amounts of each output to make a determination. Like all chain analysis heuristics the Round Amounts Heuristic is probabilistic: it cannot offer certitude.

For example, if a transaction creates two outputs in the amounts of 0.8 BTC and 0.31838477 BTC, it may be assumed that the 0.8 BTC output has been sent to another party as a payment while the second output was the change output. Likewise, if a bitcoin amount of an output is convertible to a precise and round amount in a fiat currency like USD, it may be assumed that this was a payment and not a change output.